Microphone



Oct. 31, 1933. l.. GILMAN MICROPHONE Filed April 25, 1932 Patented Oct. 3l, 1933 MICROPHONE Louis Gilman, Chelsea, Mass., assigner to Radio Television Industries Corporation, Mass., a corporation of Delaware Boston,

Application April 25, 1932. Serial'No. 607,242

6 Claims.

This invention relates to microphones and more especially to microphones for use in broadcasting.

The general object of the invention is to provide an extremely compact microphone that may be attached to the person of the broadcaster, for instance, to the lapel of his coat, and which .has suilicient sensitiveness and power to operate for its intended purpose, even although the voice waves are not directed toward the same as where, -for example, the broadcaster is addressing an audience.

Specific objects of my invention are to provide a novel means for stretching the diaphragm of the microphone so that thenatural frequency thereof will be higherthan that of the highest audible note transmitted, in order to avoid distortion, and to provide a simple and eiiective means for firmly attaching to the microphone terminals the ends of the two conductors connecting the device to the transmitting circuit.

An illustrative embodiment of my invention that has given good results in practice is shownv in the accompanying drawing in which- Figure 1 is a front view of amicrophone embodying my improvements;

Fig. 2 is a rear view thereof; v

Fig. 3 is a central section taken on the vline 3-3 of Fig. 2;

Fig. 4 is a central longitudinal section on an enlarged scale of a detail of construction, and

Fig. 5 is an under-plan view'thereof on an enlarged scale.

In the particular drawing selected for m'ore fully disclosing my invention, 10 is a disc which may be of metal, said disc having a centrallydisposed button chamber and provided with an annular rim 11. The usual button disc 13 carrying a carbon button 14 is arranged in the button chamber and is provided with a threaded stud 15 secured to the rear face thereof and co-axial therewith. In the space between the felt washer 16, button 14 and diaphragm 17 granular carbon 18 is placed. These elementsof course do not form partof the present invention and are common to all microphones.

The front face of the disc 10 consists of a flat annular portion 18' between the chamber and the rim and said front face is provided with an.

annular groove 19 adjacent the rim ll, said groove preferably having one side' levelled, as shown at 20. A

For stretching the diaphragm and holding the same in position, I provide an annulus 21 having a flange' 22 concentric with the rim l1, the inner edgeof said flange preferably being bevelled correspondingly to the edge of the ange. In the present instance the annulus is provided with a recticulated face 23'to protect the diaphragm and permit the sound waves to impinge thereon.

After the elements making up the microphone have been assembled, as hereinafter more fully set forth, the diaphragm is placed on the front face of the microphone and stretched and maintained in stretched condition by forcing the annulus 21 into the position shown in Fig. 3 where 65 it is held frictionally between the rim 11 of the button chamber and the flange 22 of the annulus. As will be obvious from Fig. 3, the diameter of the diaphragm is larger than that of the disc 10, and therefore, when the annulus'is forced 70 home, the peripheral portion of said diaphragm will be disposed between the rim 11 of the disc and the flange 22 of the annulus, as indicated at 17. A portion of said diaphragm will be forced into the annular groove 19 the bottom of which 75 is slightly inward of said flat annular portion 18' of the front face of the disc whereby a slight rim is formed on the inner face of the diaphragm, such rim assisting in maintaining the diaphragm in stretched condition. The outside diameter of the flange 22 must, of course, be smaller than' the inside diameter of the rim 11, and preferably the difference between said diameters is approximately twice the thickness of the diaphragm, or a little less, in order that the peripheral portion 8b of the diaphragm may be tightly clamped between said rim and ange. As will be apparent, the peripheral portion ofthe diaphragm is` first tightly clamped between the rim and flange and thereupon further inward movement of the annulus will force the metal of the diaphragm into the annular groove 19 and give the Acentral portion of the diaphragmthe desired tension. It will be noted that the annulus is secured to the disc solely by the conjoint frictional engagement of its ange, the annular rim of the disc and the peripheral portion of the diaphragm interposed therebetween.

While various means will readily occur to those skilled in the art for suitably connecting the ter- -ceiving a pair 'of conductors 30. The lower strip is provided with s. slot 31 extending between the 110.

eyelet holes. Preferably the eyelets are threaded and means are provided for mechanically and electrically connecting the same to the microphone terminals. In the present instance the stud which, as aforesaid, is integral with the button disc 13, has threaded engagement with the eyelet 27, whereby said eyelet is mechanically and electrically connected to said disc, which constitutes one of the microphone terminals, and a screw 32 passing through the disc l0 which is in electrical connection with the other microphone terminal, viz, the diaphragm, has threaded engagement with the eyelet 28, and thereby secures the other end of the insulating member to the disc. As indicated in Fig. 3, and shown more clearly on an enlarged scale in Fig. 4, the insulated conductors pass through the aperture 29 and the bare ends thereof are housed within the slot 31 and pass around the heads of the eyelet, respectively. It will be understood, of course, that the member 24 is secured in position on the rear face of the disc before the felt washer, granular carbon, diaphragm and annulus are assembled. The bare ends of the conductors are each given a turn around the heads of the eyelets and the member 24 then firmly clamped to the rear face of the disc 10 `by screwing the stud 15 into .the eyelet 27, turning the button disc 13 for this purpose, and then completing the attachment of said member 24 by the screw 32.

By this means the conductors are firmly clamped to their respective terminals. The washer is then placed in position, the chamber loaded with granular carbon, and the diaphragm attached and stretched in the manner above set forth. A hook 33 of any suitable design is attached in any suitable manner, as by the screws 34, to the rear face of the microphone. The conductors preferably pass over said hook and are secured to the same near the free end thereof by thread 35 wrapped around said conductors and through the'loop 36 formed in the hook 4near the free end thereof.

Suitable means, such as the insulating discs contact between the button disc and the disc 10.

The concrete embodiment of the present invention shown in the accompanying drawing is 1*/4" in diameter by 1A" in thickness, weighs about two ounces, and has been found in `actual practice to have the sensitivity and frequency range of much larger and heavier broadcasting microphones.

Having thus described an illustrative embodiment of my invention without, however, limiting the same thereto, what I claim and desire to secure by Letters Patent is;

1. A microphone comprising a disc having a centrally-disposed button chamber and an annular rim, a diaphragm disposed on the front face of said disc, and an annulus having a ange concentric withsaid rim, the peripheral portion of said diaphragm being interposed between said rim and flange and said annulus being secured to said disc solely by the conjoint trictional engagement of said flange, said annular rim and the peripheral portion of said diaphragm interposed therebetween.

2. A microphone comprising a disc having a n centrally-disposed button chamber and an annular rim, a diaphragm disposed on the front face of said button chamber, and an annulus having a-ilange concentric with said rim, the outside diameter of said annulus being smaller than the inside diameter of said rim by approximately twice the thickness of said diaphragm, the peripheral portion -of said diaphragm being interposed between said rim and ilange and said annulus being secured to said disc solelyby the conkjoint frictional engagement of said flange, said annular rim and the peripheral portion of said diaphragm interposed therebetween.

3. A microphone comprising a disc having a centrally-disposed button chamber and an annular rim, a diaphragm disposed on the front face of said disc, said front face/having an annular depression adjacent said rixn, and an annulus having a flange concentric with said rim, the peripheral portion of said diaphragm being interposed between said rim and iiange and a portion thereof lying in said depression, said annulus being secured to said disc solely by the conjoint frictional engagement of said ange, said annular rim and the peripheral portion of said diaphragm interposed therebetween.

4. A microphone comprising a disc having a centrally-disposed button chamber and an annular rim, the iront face of said disc comprising a flat annular portion between said chamber and rim, a diaphragm disposed on the front face of said disc, and an annulus having a flange concentric with said rim, one edge of said flange being bevelled, the front face of said disc having an annulargroove arranged to receive the end of said flange and one side of said groove being bevelled correspondingly to the edge of said ange, the peripheral portion of 1said diaphragm being disposed between said rim and ange and a portion thereof lying in said depression, said annulus being secured to said disc solely by the conjoint frictional engagement of said flange, said annular rim and the peripheralI portionof said diaphragm interposed therebetween.

5..A microphone comprising a disc having a centrally-disposed button chamber, a button disc in said chamber, an insulating member providedV with two spaced threaded eyelets, a stud secured to the rear face of said button disc and co-axial therewith, said stud having threaded engagement with one of said eyelets, a screw passing through said disc and mechanically and electrically connecting the second oi' said eyelets to said disc. said insulating member having an aperture intermediate said eyelets for receiving a pair of electrical conductors andY the under side thereof being slotted to house the ends thereof.

6. A lapel microphone provided with an attaching hook on the rear face thereof, an insulating member provided with two conducting members, means for electrically and mechanically connecting said conducting members to the microphone terminals, a pair of conductors having their ends disposed between said insulating member and the rear face of said microphone and connected, respectively, to said conducting members, said conductors passing over said hook, and means securing the same to said hook near the tree end thereof.

LOUIS GILMAN. 

